Who wants to discuss the benefits of running a water-only brew cycle to pre-warm the brew chamber? Well, I kinda' do. :-) When I first received my Trifecta MB last May, I religiously did water-only pre-warm cycles before the first actual brew with coffee grounds. With succeeding brews (second cup, etc.) in any brew session, I would always rinse out the brew chamber with hot tap water (135ºF) before brewing the next cup. After a few months, I lost that religion, got impatient, somewhat complacent, and didn't do the pre-warm cycles again until a few weeks ago. The colder weather and the fact that my Trifecta sits right next to the kitchen window got me thinking about this again. I decided to do a few temperature and taste tests to see if it was worth the trouble. My normal brew is 12 oz. water, 25.7 g coffee, C/:45 settings, so for the pre-warm, I left the settings the same, but didn't add any coffee grounds. The water enters the brew chamber at 200ºF. A Bunn engineer confirmed this temperature and also that the air entering the brew chamber for both turbulence and press-out is NOT heated on either the MB or the commercial version. Interestingly enough, he also mentioned that there was a plug-in port on the control board where he could adjust the water temperature to something besides 200ºF with a computer. Hmmmm! I used a Thermapen thermometer to measure the temperature of the coffee just as it was being pressed out. This measurement was made at the black plastic diverter, right under the brew chamber shelf. The highest temperatures were right as the press-out started and decreased as more air entered the brew chamber during the press-out phase. Obvious factors that would lower the brewing temperature within the brew chamber are the coffee grounds, temperature of the brew chamber and unheated air entering the brew chamber for varying turbulence cycles (number, time and force) and press-out. The following are the highest reading that I measured while using my normal brew specs. (12 oz. water, 25.7 g coffee, C/:45 settings):

Brewing with a room-temperature (70ºF) brew chamber: 182ºF - 183ºF

Brewing after a water-only, pre-warm cycle: 189ºF -190ºF

If there was this difference in the press-out temperatures, then that difference should also be reflected in the actual brewing temperature within the brew chamber, correct? I definitely noticed a difference in taste (for the better), as did another Trifecta owner I discussed this with (DanH). My feeling is that when running an initial water-only cycle to pre-warm the brew chamber, the resulting brewing temperature will be more in line with what is considered optimal for brewing coffee. YMMV depending on your taste, coffee brewed, etc. etc. I thought that this was quite interesting and started always doing the pre-warm cycles again. Has anyone else noticed this difference in taste? Just wondering. Comments?

I run a water-only brew cycle first when it is cold out, but since I live in Texas we are currently seeing temps up to the 80s daily. When you combine that along with me usually being impatient I don't usually run a water-only brew cycle. Of course I'm not taking temps once I brew but the coffee is still plenty hot that I still let it rest before drinking. And with 2 toddlers and a baby in the house a lot of times I don't get to enjoy my coffee right away, or get interrupted while drinking, so a lot of times it goes cold - which I don't mind. Therefore the extra time and effort of pre-warming would have been wasted for me. But maybe I'll try it again just to do something different.

I think that the improved taste difference comes from the higher brewing temperature. Actually, the water from my pre-warm cycle goes directly into the first cup to pre-warm it, since after brewing that one, it has to sit on the counter and wait as I brew the second cup. Sometimes I pour that heated pre-warm water from the first cup into the second cup, to pre-heat that as the first cup is being brewed. I just need to remember to empty the pre-heated water out of the first cup before the coffee cycle gets pressed out. What a mess when you forget! :-)

Thanks again for taking the trouble to measure the temps. There are so many good reasons to run an extra cycle before brewing:

If you measured the temp at the end of the brew time, you should find that the difference is even greater, owing to the heating of the brew chamber.

It's fairly well established that higher temps will dissolve the grounds quicker and produce more flavor under favorable conditions. That means that you can go with a slightly coarser grind than if the temp was lower.

I don't use soap when I wash my brew chambers. I just use hot water under fairly good pressure and wipe with a paper towel. I also give the underside of the brew chamber a blast to clear out the valve on that side. Having said that, I like the idea that a prewarm cycle also gives the brew chamber an extra hot rinse just before I use it.

And yup, for those of us who like half n half in their coffee, preheating the cup is a must.

Another thing that I just thought about that might affect the taste is the water. That which is sitting in the tank overnight, has been constantly heated over time and then another quick reheat to bring it up to 200ºF when you engage the flap again. I usually leave my side reservoir empty and then fill it with fresh filtered water for the first actual "brew". The water that has been sitting in the tank ends up being used only for the pre-heat.

As with all brewers, temperature loss occurs on the journey to the cup, carafe or pitcher. Preheating the system and your vessel is a great idea to minimize this temperature loss. Plus with trifecta you'll get the added benefit of a water only brew to flush out the check valves.

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